Triggerd primarily byill effects of polluted air, soil and water resources on living species, public concern for environmental quality has been growing during the past four decades or so. One manifestation of this concern is found in occurrence of public debates as well as in the demand for full environmental impact assessment before a water-resources project is approved. Engineering soundness and economic feasibility are no longer sufficient criteria for construction of hydraulic works. As a result, environmental considerations have become very much a part of hydraulic analyses. In response to growing environmental concerns, the field of hydraulics has expanded and a new branch, called Environmental Hydraulics, has emerged. The focus of this branch is on hydraulic analyses of those environmental issues that are important for protection, restoration, and managementof environmental quality. The motivation for this book grew out of the desire to provide a hydraulic discussion of some of the key environmental issues.It is hoped that the book would serve to stimulate others to write more comprehensive texts on this subject of growing importance.